In recent years, a HSUPA (High Speed Uplink Packet Access) is standardized as a high-speed packet data transmission method for up link, and application to a W-CDMA (Wide band-Code Division Multiple Access) system is under consideration. A HARQ (Hybrid Automatic Repeat reQuest) is adopted in a HSUPA, and minimum delay and high throughput are achieved by a high-speed retransmission control. The HARQ is a technology that improves an error correcting capability at the time of retransmission by combining an ARQ (Automatic Repeat reQuest) and an error correcting code. Further, the HARQ synthesizes decoded failed-data and re-transmitted data, and executes a decoding process.
A physical channel by which an E-DCH (Enhanced Dedicated Channel), that is a transport channel in the HSUPA, is mapped is an E-DPDCH (Enhanced Dedicated Physical Data Channel). The E-DPDCH is used with an E-DPCCH (Enhanced Dedicated Physical Control Channel) which is a control channel for transmitting control information on a physical layer. And, 2 ms and 10 ms are specified as an E-DCH TTI (Transmission Time Interval).
A RSN (Retransmission Sequence Number) which is information indicating number of retransmissions required for the HARQ is transmitted on the E-DPCCH. The RSN is composed of 2 bits and from “0” to “2” indicates number of the retransmissions, and “3” indicates that number of the retransmissions is no smaller than three (3 times). In other words, when the RSN is any one of “0”, “1”, and “2”, it can specify number of the retransmissions. However, when RSN equals 3, it cannot specify actual number of the retransmissions.
In addition, an acknowledgement message (Acknowledgement) is transmitted after signature multiplexed by an E-HICH (E-DCH Hybrid ARQ Indicator Channel). When the TTI equals 10 ms, the acknowledgement messages are transmitted in total of 5 times for every 2 ms (every sub-frame) on the E-HICH.
On the other hand, when it performs a handover by a different frequency carrier between the same communication systems or different communication systems, a mobile station receives signals of other frequencies during the communication. And the mobile station needs to measure a required signal level and to receive required control information in order to change a communicating base station.
In the W-CDMA system, transmission information of the usual mode is transmitted in a short period by time-compressing and a non-transmitting gap (GAP) is created. And the W-CDMA system has a compressed mode where other frequency carriers are monitored by using the GAP. The W-CDMA system monitors information from the base stations which belong to the same cell and to its adjacent cells by using the compressed mode.
FIG. 1 is a conceptual diagram showing a transmission status of the re-transmitted data of the E-DPDCH in a case that the TTI equals 10 ms during the compressed mode. Numbers “0”, “1”, “2”, and others described in FIG. 1 are serial numbers that are assigned to time slots of transmitted data. In the HSUPA, the mobile station should not transmit any data during the compressed mode is initiating and also at a section that is overlapping with GAP, when the TTI equals 2 ms. In a case that the TTI equals 10 ms and the compressed mode is overlapping with GAP at an initial transmission, the mobile station transmits using a time slot which does not overlap with the GAP as shown in FIG. 1(a).
In addition, at a retransmission, the mobile station transmits using a time slot which is not overlapped with the GAP at a current transmission section as shown in FIGS. 1 (b), (c) and (d). When available time slots are more than the time slots for the initial transmission, then the excess time slots are set as DTX (Discontinuous Transmission) as shown in FIGS. 1 (c) and (d). When available time slots are less than the time slots for the initial transmission, then it does not transmit the data of the insufficient time slot as shown in FIG. 1 (b).
Then, some technical literatures in relation to the above-mentioned descriptions are explained as follows. The following (1) to (4) are conventional standards that relate to the data retransmission of the E-DPDCH which has been described above.    (1) 3GPP TS25.214 V6.11.0 (2006 December)    (2) 3GPP TS25.214 V7.7.0 (2007 November)    (3) 3GPP TS25.212 V6.10.0 (2006 December)    (4) 3GPP TS25.212 V7.7.0 (2007 November)
In addition, a Japanese Patent Application Laid-Open No. 2004-032640 discloses a technological example of reducing number of retransmissions at a time of handover. A Japanese Patent Application Laid-Open No. 2006-191312 discloses a technological example of detecting packet losses while initiating the compressed mode and executing the retransmission and other processes. A Japanese Patent Application Laid-Open No. 2006-222494 discloses a technological example of transmitting dummy ACK in order to start a retransmission control.
A Japanese Patent Application Laid-Open No. 2006-245838 discloses a technological example of signature multiplexing and transmitting information to the mobile station. A Japanese Patent Application Laid-Open No. 2007-082192 discloses a technological example of retransmitting a packet in a case that the E-DCH TTI equals 10 ms. A Japanese Patent Application Laid-Open No. 2007-129673 discloses a technological example of retransmitting missing packets when packets are not precisely combined. A Japanese Patent Publication No. 3913259 discloses a technological example of transmitting a plurality of data using an exclusive signature number on an independent channel.